A study of the metabolic consequences of administration of diuretics to dogs in vivo is in progress. Total renal CO2 production, C14O2 production from C14-labeled glucose infused i.v. and proportion of total CO2 derived from glucose are measured in conjunction with rate of sodium excretion. This study is designed to test whether that fraction of sodium reabsorption which is blocked by the diuretics furosemide, thiomerin and acetazoleamide is energy dependent and whether glucose supplies any major fraction of that energy. A study of the metabolism of glutamine by the perfused rat kidney is contemplated as the next project. Glucose, amino acids, and fatty acids (all at physiological concentrations) will be added to the perfusion medium. Glutamine in concentrations of 0.5 micromolar (physiological), 3.0 micromolar, and 10.0 micromolar will be added to the medium to test whether the supernormal concentrations of glutamine usually added in in vitro studies alters the proportions directed to glucose production and to CO2 production.